1. Field of the Invention
The present disclosure relates to an arc extinguishing unit of a molded case circuit breaker (MCCB), and more particularly, to an arc extinguishing unit of an MCCB having a structure in which grids and side plates forming an arc chamber are coupled in an inserted manner, facilitating an operation, and intervals of grids are uniformly maintained and a configuration of the grids is not damaged, thus maintaining stable performance and allowing for maintenance.
2. Background of the Invention
In general, an MCCB is an electric device for automatically breaking a circuit in an electrically overloaded or in the event of a short-circuit accident to protect circuits and a load. An MCCB includes a terminal unit allowing for connection between a power source side and a load side, a mechanism unit opening and closing a stator and a mover to be mechanically brought into contact, a trip unit sensing an overcurrent or a short circuit current flowing from a power source and inducing the mechanism unit to perform trip operation, and an arc extinguishing unit for extinguishing an arc generated when a fault current is interrupted.
A short circuit current intended to be interrupted in an MCCB is a current greater by tens of times than a rated current of the MCCB, and a short circuit current sufficient for the MCCB to interrupt is an interrupting capacity. An MCCB limits a short circuit current to a current level lower than a predetermined current to interrupt a current, and this is called current limitation interruption. In general, an MCCB has current limitation performance in proportion to arc extinguishing capability of an arc extinguishing unit and in inverse proportion to an operating time of a mechanism unit.
Performing tripping in the event of a fault current and extinguishing an arc and discharging it are the main functions of an MCCB to interrupt a fault current to protect a product, a load, and a line and are directly connected with performance of the MCCB. An arc chamber of an arc extinguishing plays a key role in the performance, and an assembled state of the component, maintaining an assembled configuration, a position thereof, and the like, significantly affect performance of the MCCB.
Korean Utility Model Registration No. 20-0462420 entitled “Arc extinguishing unit of Small MCCB” and Korean Utility Model Registration No. 20-0393296 entitled “Arc extinguishing unit of MCCB” may be referred to as related art arc extinguishing mechanisms.
FIGS. 1 through 5 illustrate an example of a related art. FIG. 1 is a cross-sectional view illustrating a single pole breaking unit of an MCCB including an arc extinguishing unit according to a related art, FIG. 2 is a perspective view illustrating a part of the arc extinguishing unit in the single pole breaking unit of FIG. 1, FIG. 3 is a partially exploded perspective view of the arc extinguishing unit of FIG. 1, FIG. 4 is an assembled view of the arc extinguishing unit of FIG. 1, and FIG. 5 is a perspective view of a grid of FIG. 4.
When a rate current flows in an arc extinguishing mechanism, a stator 102 and a mover 103 are maintained in a contact state, but when a fault current such as an overcurrent or a short circuit current is generated, the mover 103 is separated from the stator 102 by electrodynamic repulsion force generated between a fixed contact of the stator 102 and a movable contact of the mover 103, interrupting the current.
The moment the mover 103 is separated, an arc is generated between the fixed contact and the movable contact, and the generated arc is induced by an arc runner to be moved to an arc chamber 121. In this case, the arc is divided by a grid 122 of the arc chamber 121 to allow an arc voltage to be increased to be higher than a source voltage, thus limiting the short circuit current to extinguish the arc.
As for a configuration of the arc chamber 121 in the related art, the arc chamber 121 includes a plurality of grids 122 arranged at predetermined intervals in an outer side of a casing 101 from a rotary trace of the mover 103, a pair of side plates 123a coupled to both sides of the grids 122, hybrid fixing plates 123 extending from the side plates 123a, and lateral magnets 128 coupled to rear surfaces of the hybrid fixing plates 123.
Here, the hybrid fixing plates 123 are fixed to the grids 122 such that protrusions 122a of the grids 122 are respectively inserted into holes 123b of the side plates 123a, so as to be fixed in a caulking manner.
In this case, however, the caulking operation may cause the grids 122 to be deformed, broken, twisted, or the like, and the grids 122 may be released due to a defective caulking operation or omission during transportation or when an end product is assembled. In addition, since the caulking operation is performed a plurality of times, a processing time is lengthened, productivity is degraded, grid intervals of the grids 122 are poorly maintained, and the like, and production costs are increased. In addition, maintenance is not possible.